Triple‐stimulation technique improves the diagnosis of chronic inflammatory demyelinating polyradiculoneuropathy

Introduction: A difficult clinical situation occurs when a chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) patient does not fulfill any of the diagnostic criteria. Moreover, nerve conduction studies (NCS) can be consistent with axonal neuropathy and lead to misdiagnosis. Methods: We aimed to assess the usefulness of the triple‐stimulation technique (TST) for detection of proximal conduction blocks (CBs) in patients with axonal‐like CIDP. Four patients with axonal‐like CIDP were studied and compared with 10 typical CIDP patients. In the axonal‐like group, NCS showed a decrease in compound muscle action potential amplitude without features of demyelination, but nerve biopsy showed features of demyelination in all 4. Results: Twelve nerves were tested with TST, and 8 CBs were detected between the root emergence and the Erb point in the 4 patients, all of whom improved after treatment with intravenous immunoglobulin. Conclusion: TST can identify very proximal CBs in CIDP. The sensitivity of nerve conduction studies may be improved by TST in CIDP. Muscle Nerve 51: 541–548, 2015     

Proximal conduction block in the pharyngeal–cervical–brachial variant of guillain–barrÉ syndrome

Introduction: Conduction block (CB) has been included in the Rajabally criteria for axonal Guillain–Barré syndrome (GBS). Because the nerve roots may be affected early in GBS, detection of proximal CB by the triple stimulation technique (TST) can be useful. Methods: We describe TST findings in 2 patients who presented with the pharyngeal–cervical–brachial (PCB) variant of axonal GBS. Results: In the first patient, although conventional nerve conduction studies (NCS) did not fit electrodiagnostic criteria for axonal GBS, the TST detected proximal CB in the median and ulnar nerves. In the second patient, NCS fulfilled criteria for axonal GBS, and the TST detected proximal CB in the median nerve. After plasmapheresis, NCS and TST findings were normalized, suggesting reversible conduction failure rather than demyelinating CB. Conclusion: The TST may be useful for diagnosis of PCB when NCS remain inconclusive. The technique provides additional clues for classifying PCB into the acute nodo‐paranodopathies. Muscle Nerve 52 : 1102–1106, 2015     

Activity-dependent conduction block in multifocal motor neuropathy

Previous studies suggested that activity-dependent conduction block (CB) contributes to weakness in multifocal motor neuropathy (MMN). Obtaining more robust evidence for activity-dependent CB is important because it may be a novel target for treatment strategies. We performed nerve conduction studies in 22 nerve segments of 19 MMN patients, before and immediately after 60 seconds of maximal voluntary contraction (MVC) of the relevant muscle. We employed supramaximal electrical stimulation, excluded nerves with marked axonal loss, and adopted criteria for activity-dependent CB. Per segment, the segmental area ratio [area proximal compound muscle action potential (CMAP)/area distal CMAP] was calculated and, per nerve, total area ratio (area CMAP at Erb's point/area distal CMAP) was obtained. MVC induced no changes in mean area ratios and induced no activity-dependent CB. In segments with CB before MVC, the MVC induced increased duration prolongation. In MMN, MVC induced temporal dispersion but no activity-dependent CB.     

Motor nerve conduction study in cauda equina with high-voltage electrical stimulation in multifocal motor neuropathy and amyotrophic lateral sclerosis

In this study we aim to establish a motor nerve conduction study (NCS) for the cauda equina and examine its usefulness in multifocal motor neuropathy (MMN) and amyotrophic lateral sclerosis (ALS). NCS of the tibial nerve proximal to the knee was performed with an optimized high-voltage electrical stimulation (HV-ES) method in 21 normal subjects, 5 with MMN, and 11 with ALS. HV-ES, but not magnetic stimulation, could supramaximally stimulate the cauda equina. Cauda equina motor conduction time determined by HV-ES, but not that with F-waves, correlated well with cauda equina length on magnetic resonance imaging. HV-ES revealed proximal lesions in 4 MMN patients but in none of the ALS patients. Importantly, 1 patient with "MMN without conduction block (CB)" had a CB in the cauda equina. Cauda equina motor conduction is better evaluated by HV-ES than with F-wave study or magnetic stimulation. HV-ES can help to distinguish MMN and "MMN without CB" from ALS.     

Magnetic stimulation using a triple-stimulation technique in patients with multifocal neuropathy without conduction block

It has been suggested previously that multifocal motor neuropathy (MMN) without conduction block (CB) or other features of demyelination is axonal in nature. Conventional transcranial magnetic stimulation (TMS) and the triple-stimulation technique (TST) performed on 10 MMN patients without CB revealed a proximal focal CB in 4 patients. In 3 other patients, the amplitude ratio obtained in response to conventional TMS was abnormally low, but the area ratio was normal. The TST amplitude ratio and area ratio were normal in these 3 patients. This pattern suggested the occurrence of temporal dispersion without CB. The occurrence of temporal dispersion or CB was associated with a relatively satisfactory response to intravenous immunoglobulins. These findings suggest that some forms of MMN previously thought to be axonal are in fact proximal variants of MMN with CB.     

位移技术在运动神经传导阻滞测定中的价值

目的探讨位移技术在运动神经部分传导阻滞(CB)诊断和鉴别诊断中的价值。方法在30名健康对照、44例肌萎缩侧索硬化症、38例脱髓鞘疾病患者同时进行常规节段的运动神经传导速度测定和位移技术测定,对检测结果进行分析。结果在健康对照,采用常规节段和位移技术测定均未检测到CB;在肌萎缩侧索硬化症患者中,常规节段检测时在4例患者中发现2处CB、2处可能的CB,但采用位移技术进一步测定时,未检测到短节段的CB;在脱髓鞘疾病,采用常规节段检测未能达到CB标准的18根神经中,采用位移技术检测时在13根神经发现存在短节段的CB。结论位移技术可以提高CB诊断的准确率;并有助于鉴别相位抵消和传导阻滞,有利于肌萎缩侧索硬化症和脱髓鞘疾病的鉴别。     

Detection of proximal conduction blocks using a triple stimulation technique improves the early diagnosis of Guillain–Barré syndrome

Objective

Current diagnostic electrophysiological criteria can miss the early stages of Guillain–Barré syndrome (GBS). We evaluated the diagnostic efficiency of the triple stimulation technique (TST) in highlighting proximal conduction blocks (CBs) in patients who do not meet the electrophysiological criteria for GBS.

Transcutaneous cervical root stimulation in the diagnosis of multifocal motor neuropathy with conduction block

OBJECTIVES: To determine if transcutaneous electrical stimulation of the cervical roots can be used to diagnose proximal conduction block (CB) in multifocal motor neuropathy (MMN) and whether it can reliably distinguish MMN from amyotrophic lateral sclerosis (ALS). METHODS: Compound muscle action potentials (CMAPs) over the abductor digiti minimi (ADM) were evoked by supramaximal stimulation of the ulnar nerve at the wrist, below elbow, above elbow, axilla, Erb's point, and C8/T1 cervical roots in three groups of patients: 31 patients with ALS, nine patients with MMN, and 31 controls. Supramaximal stimulation at Erb's point and the C8/T1 roots was carried out using a transcutaneous high voltage electrical stimulator. The negative peak amplitude, area, and duration of the CMAP were measured and normalised to that from the wrist. The percentage change in each segment in these parameters was calculated and compared between the different groups. RESULTS: At stimulation sites proximal to the elbow, there were no significant differences in relative CMAP amplitude, area, or duration between controls, ALS patients, and MMN patients with clinically unaffected ulnar nerves. Similarly, the percentage segmental change between adjacent stimulation sites showed no significant differences. In six studies of MMN patients with weakness in ulnar hand muscles, the decrease in CMAP amplitude between the C8/T1 roots and Erb's point exceeded the mean + 2 SD of the control data. CONCLUSION: Cervical root stimulation can quantify CB in the most proximal segment of the ulnar nerve, a fall in CMAP amplitude if greater than 25%, indicating block, and should be used routinely in the evaluation of patients suspected of having MMN, especially when distal stimulation has proved unhelpful.     

Short-segment nerve conduction studies in ulnar neuropathy at the elbow

The aim of the study was to assess the diagnostic value of short-segment nerve conduction studies (NCS) at 2-cm intervals from 4 cm above to 4 cm below the medial epicondyle in a large group of patients with ulnar neuropathy at the elbow (UNE). Furthermore, we wanted to compare electrodiagnostic and clinical findings. We evaluated 73 arms in 70 patients with UNE and observed the following abnormalities on short-segment NCS: focal conduction block (CB) in 1, focal CB with increased latency change in 34, and increased latency change alone in 25. Short-segment NCS had an additional localizing value in 28 arms of the 37 patients (76%) with motor conduction velocity (MCV) slowing across the elbow only or with nonlocalizing electrodiagnostic findings. The lesion was located above the elbow in 32 arms (53%), at the epicondyle in 16 arms (27%), and below the epicondyle in 12 (20%) of the 60 arms with focal CB or increased latency change on short-segment NCS. Patients with CB on routine and short-segment NCS had muscle weakness significantly more often than patients without CB. Thus, short-segment NCS are useful in localizing the lesion in patients with UNE and CB on routine NCS and have additional diagnostic value in patients with MCV slowing across the elbow or with nonlocalizing signs on routine nerve conduction studies. We recommend its use in all patients in whom UNE is suspected.     

Persistent multifocal pseudo‐conduction blocks in vasculitic neuropathy without antiganglioside antibodies

A woman presented with severe multifocal acute axonal neuropathy due to necrotizing vasculitis. Six years later, electrophysiological examination revealed features suggestive of persistent conduction block (CB) with increased temporal dispersion (ITD) affecting the right median and tibial nerves. A clinical case characterized by multifocal CBs that were observed several years after an initial episode of vasculitic neuropathy was recently reported. The occurrence of CBs paralleled clinical deterioration and was attributed to superimposed antiganglioside antibody‐mediated demyelination. In contrast, our patient was clinically stable and did not have antiganglioside antibodies. Nerve conduction studies showed pseudo‐CBs rather than true CBs. We suggest that pseudo‐CBs with ITD can reveal heterogeneous axonal regeneration as a sequel of a severe multifocal vasculitic neuropathy. This condition should be distinguished from the occurrence of pseudo‐CB in the acute phase of vasculitis or from superimposed immune‐mediated demyelination. Muscle Nerve 40: 290–293, 2009     

Motor neuropathy with proximal multifocal persistent conduction block, fasciculations and myokymia. Evolution to tetraplegia

We describe a patient with chronic asymmetric motor neuropathy, which began in the upper extremity. The paretic muscles showed abundant fasciculations and myokymia but only little amyotrophy. Electrophysiologic examination revealed proximal multifocal persistent conduction block (CB) not located at the usual entrapment sites, and arrhythmic isolated or grouped fasciculation potentials originating distally on blocked axons. Over the years, new CBs developed, which led to tetraplegia, and amyotrophy slowly increased with progressive denervation. This patient differs from the cases of chronic acquired demyelinating polyneuropathy described in the literature by the absence of sensory deficit and the proximal location of CB.     

Proximal nerve conduction studies in chronic inflammatory demyelinating polyneuropathy.

OBJECTIVE: The purpose of this study was to evaluate the sensitivity and specificity of proximal upper limb motor nerve conduction study abnormalities in chronic inflammatory demyelinating polyneuropathy (CIDP), using standard percutaneous stimulations up to Erb's point. METHODS: Electrophysiologic data relating to proximal conductions of median and ulnar nerves of 22 patients with CIDP were retrospectively analyzed and compared to those of 22 controls with sensory neuropathy. Distal conduction results were also reviewed. RESULTS: The findings demonstrate independent high sensitivity of abnormal upper limb proximal nerve conduction studies in CIDP. Demonstration of conduction block of >20% and temporal dispersion of >15% had low specificity. However, conduction block was highly specific with cut-off values of >30% at axilla and >50% at Erb's point. Specificity was considerably improved using a cut-off value of >30% at proximal levels for temporal dispersion. Diagnostic sensitivity improved significantly with proximal studies with the criteria used in this population. No adverse effects had occurred as result of proximal stimulations. CONCLUSIONS: Proximal studies are safe, sensitive and reliable procedures in cases of suspected CIDP. Their use appears justified although adequate cut-off values are desirable to optimize their specificity. SIGNIFICANCE: This study indicates that proximal upper limb nerve conductions are appropriate in investigating suspected CIDP, as detailed in recently established electrophysiologic criteria. However, specificity is largely dependent on cut-off values for conduction block and temporal dispersion.     

Sensory conduction study in chronic sensory ataxic neuropathy.

Sensory conduction was studied in six patients with chronic sensory ataxic neuropathy of an idiopathic type and associated with Sjögren's syndrome. Motor nerve conduction velocities were normal in most cases, but sensory nerve potentials could not be evoked in a routine peripheral nerve conduction study. Cortical and cervical somatosensory evoked potentials (SEPs) and evoked potentials from Erb's point were barely recorded by median nerve stimulation at the wrist. When the median nerve was stimulated at more proximal points, clear potentials were recorded from Erb's point, but cortical SEPs were still hardly elicited. Thus the sensory nerves are centrally and peripherally involved in this condition, and the involvement is more prominent in the distal portion in the peripheral nerve. These findings suggest that central-peripheral distal axonopathy is a process involved in this illness and that the dorsal root ganglia may be primarily involved, in accord with previous pathological studies.     

Peroneal neuropathy after weight loss

The objectives of this study were to evaluate the clinical and electrophysiological findings in peroneal mononeuropathies following a weight-reduction diet. Thirty patients with acute peroneal palsy and weight loss were studied. Complete nerve conduction studies (NCS) were performed in upper and lower limbs. NCS showed conduction block (CB) of the peroneal nerve at the fibular head that recovered in 29 patients within 3 weeks to 3 months. Severity of CB was correlated with clinical weakness. Three patients had abnormalities consistent with polyneuropathy (PNP). NCS in asymptomatic relatives confirmed familial neuropathy. Nerve biopsy and molecular study were consistent with hereditary neuropathy with liability to pressure palsies (HNPP). One of these peroneal palsies (6 months) recovered after neurolysis. Weight loss might be a risk factor in peroneal mononeuropathies. NCS is a tool in the diagnosis of the site and severity of the nerve injury. Testing should be considered for relatives of patients with PNP because peroneal mononeuropathies may be the first expression of HNPP.     

Acute-onset painful upper limb multifocal demyelinating motor neuropathy

We report three patients who presented with acute onset of shoulder and upper arm pain followed within a few days by predominantly distal upper limb weakness. Nerve conduction studies showed severe and unequivocal focal motor conduction block in the forearm and/or upper arm along with slowing of motor conduction and prolonged F wave responses. Only very mild changes in sensory nerve conduction were found. One patient made partial clinical improvement after 17 months, and there was a significant improvement in the degree of motor conduction block and the motor conduction velocities. A second patient remained unchanged after 5 months. Idiopathic brachial neuritis (IBN) typically presents acutely with brachialgia and acute or subacute non-progressive weakness. Multifocal motor conduction block in nerves in the arm or forearm has not been described in patients with IBN. Multifocal motor conduction block restricted to the upper limbs has been described in focal chronic inflammatory demyelinating polyneuropathy (CIDP) and in multifocal motor neuropathy with multifocal motor conduction block (MMNCB). However, both these conditions have hitherto usually been described as largely painless chronic progressive disorders with a subacute onset. Our patients, with features overlapping MMNCB/CIDP and IBN, represent an as yet unreported clinical variant. Received: 9 February 2000 / Received in revised form: 18 May 2000 / Accepted: 28 June 2000     

A practical definition of conduction block in IvIg responsive multifocal motor neuropathy

BACKGROUND: Multifocal motor neuropathy with conduction block (MMN) can be mistaken for motor neurone disease or other lower motor neurone syndromes, but is treatable with intravenous immunoglobulin (IvIg). Formal electrophysiological criteria for conduction block (CB) are so stringent that substantial numbers of patients may miss out on appropriate treatment. METHODS: Electrophysiological data were collected from 10 healthy volunteers and compared to data from 10 patients who satisfied the clinical criteria for MMN and who responded to IvIg. This produced a definition of CB in MMN patients which was compared with existing definitions to assess "miss rates". RESULTS: Mean values for compound muscle action potential area, amplitude, and duration were calculated in normal subjects. Results beyond 3 SD of their respective means were considered abnormal. Using these criteria, CB in the context of MMN was defined as a reduction in negative peak area >23% along a distal nerve segment or >29% across a proximal segment; or a reduction in amplitude >32% across a distal segment or >33% across a proximal segment. All IvIg responsive patients had at least one nerve segment showing such CB. Employing some criteria from the literature would have denied treatment to over 30% of responsive patients. CONCLUSION: In the clinical setting of suspected MMN, less stringent criteria for CB can improve the diagnosis of this treatable disorder. Exclusions on grounds of temporal dispersion may be over-restrictive. A little over one third of CBs occur proximally.     

多灶性运动神经病的临床表现及肌电图特征

目的 探讨多灶性运动神经病(multifocal motor neuropathy,MMN)的临床表现及肌电图(electromyography,EMG)特征.方法 选择2016 年6 月至2019 年12 月南京医科大学附属南京医院(南京市第一医院)收治的7 例MMN 患者,对其临床资料及神经电生理检查结果进行回顾性...     

Do GM1 antibodies induce demyelination?

We review clinical, neurophysiological, immunological, and experimental data concerning multifocal motor neuropathy (MMN), a newly recognized disorder that mimics MND. It is separated from MND by the presence of multifocal conduction block (CB) demonstrated electrophysiologically, and in some instances by the association of high liters of GM₁ antibodies. The possible immunopathogenetic effect of GM₁ antibodies is discussed. However, 70% of patients with MMNCB do not have elevated titers of GM₁ antibodies, but may respond nevertheless to immunosuppressive treatment. Thus, so far unrecognized antibodies may react against some other epitopes in the paranodal region than those attacked by GM₁ antibodies to cause CB. © 1994 John Wiley & Sons, Inc.     

Multifocal acquired demyelinating neuropathy masquerading as motor neuron disease

We report five patients with pure motor neuropathy characterized by multifocal weakness, muscle atrophy that was sometimes profound, cramps, and fasciculations with relatively preserved reflexes. The clinical picture led to an initial diagnosis of motor neuron disease in all cases, but nerve conduction studies revealed multifocal conduction block confined to motor axons and predominantly involving proximal nerve segments. Routine sensory nerve conduction studies, ascending compound nerve action potentials, and somatosensory evoked potentials were all normal even through nerve segments in which motor conduction was severely blocked. Onset of symptoms was insidious, and progression was indolent. In two cases, after many years of neuropathy, sensory abnormalities developed but remained clinically trivial. These unusual cases probably have the same pathogenesis as previously described patients with persistent multifocal conduction block. Distinction from motor neuron disease is critical, since chronic demyelinating neuropathy may respond to treatment.     

Central motor conduction time in patients with multifocal motor conduction block.

The finding of conduction block (CB) within short consecutive segments along a motor nerve is a key feature of multifocal motor neuropathy (MMN). Despite their different pathogenesis, this may be the only clinical difference between some cases of MMN and the pure spinal muscular atrophy form of motor neuron disease (MND). In 12 patients with distal atrophy and fasciculations and electrophysiological evidence of CBs in the upper limbs, we measured the peripheral and central motor conduction times (PMCT and CMCT) to hand muscles. We reasoned that patients with MMN should show an abnormally prolonged PMCT with normal CMCT, whereas an increased CMCT would suggest MND. All patients had delayed F-wave latency and increased PMCT. Three patients had increased CMCT. Follow-up showed little clinical and electrophysiological change in 7 of the 9 patients with normal CMCT, and a progressive motor deficit leading ultimately to death in 1 of the 3 patients with increased CMCT. This patient's electrophysiological follow-up showed a significant decrement of the compound motor action potential to both proximal and distal stimulation points, with disappearance of earlier CBs. Autopsy revealed loss of anterior horn cells and axons of the ventral root, and degeneration of large myelinated fibers. We conclude that determining the CMCT may help in differentiating MND from MMN. Persistence of a stable clinical picture over a span of at least 1 year and lack of electrophysiological signs of involvement of upper motor neurons should both be required before establishing the diagnosis of MMN even with electrophysiological evidence of CB.